A Radio Frequency (“RF”) connector is an electrical connector designed to work at radio frequencies. RF connectors are typically used with coaxial cables and are designed to maintain the shielding that the coaxial cable offers.
FIG. 1a, 1b and 1c illustrate a conventional surface-mounted RF connector 100. The conventional RF connector 100 generally has a center conductor 110, an insulator 120, a shielding shell 130, and a connector body 132. The shielding shell 130 is externally mounted on the insulator 120, and the center conductor 110 is partially inserted into a central insertion bore of the shielding shell, through a conductor receiving passageway formed on a mating end of the shielding shell 130.
Generally, the RF connector 100 is surface-mounted on a circuit substrate such as a printed circuit board (“PCB”) 200 (See FIG. 2) via the center conductor 110 and four solder legs 131. More specifically, the four solder legs 131 are soldered into the corresponding solder leg receiving holes 250 disposed in the printed circuit board 200. The center conductor 110 is soldered to a corresponding solder pad 240 in the center of the printed circuit board 200 via a cylindrical shaped solder terminal.
The connector body 132, center conductor 110, air between the body 132 and an exposed soldering tip 111 of the center conductor 110 together form a coaxial structure, which has a characteristic impedance higher than 50 Ohm. This impendence discontinuity often causes big reflections on signal transmission. As a result, the voltage standing wave ratio (“VSWR”) will be high, especially at a higher working frequencies. Therefore, as shown in FIG. 1c, the characteristic impedance of the conventional RF connector is not continuous, because a transition portion 104 of the traditional RF connector 100 has a higher characteristic impedance than other portions of the RF connector 100.
Consequently, the signals transmitted between the conventional RF connector 100 and the PCB 200 are poorly shielded as opposed to the coaxial cable, which would adversely affect the impedance continuity at the center conductor 110.
There is a need for an improved shielding shell to form a better coaxial structure, so as to improve the VSWR of transmitted signals.